#include <stdio.h>
int main(){
    unsigned int m=0,s=0,t=0;
    scanf("%u%u%u",&m,&t,&s);
    if(t!=0){
        if(m-s*1.0/t>=0) printf("%u",(int)(m-s*1.0/t));
        else printf("%u",0);
    }else printf("%u",m);
    return 0;
}